1. Field of the Invention (Technical Field)
The present invention relates to methods and apparatuses employing plasmonic materials for extraordinary light transmittance through optically thick metal films and other ways to control light, particularly for use in optical devices.
2. Background Art
Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
All-optical logic systems to replace semiconductor-based systems are becoming an increasingly important goal as the inherent physical limitations of electronic systems are approached. Stable and error-free optical components, including optical gates, optical switches, optical transistors, and optical filters, are required by such all-optical logic systems. The present invention provides such devices and underlying methods of accomplishment.
The existing art, represented by the following United States patent documents, are usefully divided into five groups:
1. Devices in which quantum wells are used to achieve manipulation of one laser beam by another.
2. Devices used to achieve great spatial resolution in optical object imaging.
3. Devices using arrays of subwavelength holes to achieve optical filtration or other related goals.
4. Electrooptical devices.
5. Amplitude to phase conversion logical devices.
Group 1 comprises U.S. Pat. Nos. 4,528,464, 5,485,014, 5,016,990, and 6,172,793. Each of these employ semiconductor quantum wells, which the present invention does not employ. Moreover, optical switches which are based on the confined Stark effect in quantum wells are much slower then switches which are based on the Kerr effect, as described in the present application.
Group 2 comprises U.S. Pat. Nos. 5,789,742, 5,969,345, and 4,659,429. The devices described obtain high spatial resolution when doing optical microscopy and lithography.
Group 3 comprises U.S. Pat. Nos. 6,040,936, 5,973,316, 6,236,033, and 6,285,020. The devices described use perforated metal films for selective optical transmittance, light intensity modulation, and related functions. However, all the devices described require holes (or modulation in the metal film) to be periodic. The present invention does not require any hole periodicity to achieve the goals of selective optical transition or related functions. The present invention depends only on the spatial periodicity of perturbation of refractive index, eliminating the need for periodically perforated metal films.
Group 4 comprises U.S. Pat. No. 5,155,617. The device described in the patent provides selective reflectance or absorbance controlled by applied electric field. As opposed to the present invention, this device is incapable of transmitting the light through it and of being controlled by another light pulse.
Group 5 comprises U.S. Pat. No. 5,466,925. The device described in this patent is used to convert amplitude-modulated input into phase-modulated output. Such a device is deemed to be capable of implementing AND, OR, and NAND operations for an optical computer. The device is not capable of optical circuiting, optical switching, or selective optical transmission.